Most known speedometers for vehicles, commonly known as "eddy-current drag cup speedometers", are mechanical magnet-type speedometers wherein eddy currents can be induced by the movement of a permanent magnet within an iron cup. In these known speedometers when the vehicle is moving, the permanent magnet is driven by the engine through a flexible shaft. The speed is indicated by the deflecting angle of a needle which is driven by the torque produced by interaction between the eddy current and the magnet. A few electric speedometers have been used in cars, however, they cannot provide real-time speed signals which can be used to record and control speed. In addition, current speedometers provide only the speed measurement function rather than multifunctions. In other words, current electric speedometers do not include means for connecting to other control options in order to form a speedometer with various control functions. Particularly, the unchanged mechanical magnet-type speedometer is not compatible with the rapid development in the vehicle industry because of its single function, and cannot keep pace with the trend of electrifying and automating in the vehicle industry.